In a physical environment, such as on a desk or table, an individual may utilize certain areas for placement of documents for convenient viewing. The surface area on the desk used to support the documents for viewing may be termed a workspace. Because the physical space on a desk for working is limited multiple documents may be spread out or arranged in some systematic manner within the workspace. When multiple documents require more surface area than the available area of the workspace, documents may be stacked, within the workspace, with identifying portions being visible.
In a computer system, the workspace for viewing documents or applications is the display screen or monitor of the computer system. The operating system of the computer system generally manages or controls the documents or applications displayed on the monitor. Early computer systems displayed only one document or application on the display screen at a time, therefore limiting the effective computer workspace. In order to switch among multiple applications or documents, the user had to close the application or document being displayed and open a different application or document. Such a computer system was cumbersome. With the introduction of multi-tasking and graphical interfaces, the display screen was divided into multiple portions generally referred to as windows. A window is a portion of the display screen that may contain its own document or message.
In window-based programs, the screen can be divided into several windows, each of which has its own boundaries and can contain a different document. The operating system controls these specially delineated window areas of the screen. Each window can act independently, as if it were a virtual display device. In window display environments, the windows may be resized and moved around on the display screen. Thus, with the advent of window-based programs, the computer screen workspace became more flexible. The ability to resize and move windows as well as to overlay or stack windows on top of each other essentially provided the same type of workspace available on a physical two-dimensional tabletop workspace except on a smaller scale.
Present day computer systems often employ "object-oriented" displays with windows, icons, pictures, text, pop-up or drop-down menus, dialog boxes, and other graphical items or objects in what is known as a "Graphical User Interface" ("GUI"). In such systems, various combinations of graphical items or objects are utilized to convey information to users via the monitor or display. Users interact with the computer system by activating graphical items or objects on the display. The graphical items or objects are often activated by pointing at them with a cursor controlled by a mouse or pen and clicking a control button on the mouse or pen.
An example of a computer graphical user interface that uses icons and windows is the Microsoft "WINDOWS".TM. operating system manufactured and sold by the assignee of the present invention, Microsoft Corporation. Common user interfaces such as those found in the Microsoft "WINDOWS" operating system and other GUI-based computer systems typically rely on a keyboard and a pointing device with buttons such as a mouse or trackball for user interaction. The user points to a location on the screen where an action is desired, and invokes a command by pressing a button on the pointing device or entering a keyboard command.
Just as a physical desktop table can become cluttered when multiple documents are being viewed, a computer screen workspace can become cluttered when multiple documents are displayed in multiple windows. With limited working space or viewing area on a computer screen, the computer screen workspace can quickly become cluttered if several applications or windows are opened at the same time. A number of techniques have been used for overcoming the small-screen problem presented when using computer displays.
Four general categories of computer screen workspace enhancement techniques are: (1) alternating screen uses, (2) distorted views, (3) large virtual workspaces, and (4) multiple virtual workspaces. Alternating-screen use is similar to windows in that the user can switch or change the allocation of screen space from one application to another. Some early alternating screens use techniques only allowed one application to be visible on a screen at a time. With distorted views, documents or applications appearing on the screen may be distorted to small icons. Here, applications are reduced to small pictures or icons that remind the user of the original window. Overlapping or stacked windows may also be considered a distorting technique. As noted above, when many windows overlap the appearance on a display screen may become cluttered.
With large virtual workspaces, the set of objects, the documents, or applications are organized as a large virtual workspace which cannot all be viewed on a display screen simultaneously. In one example application, the data is arranged in two dimensions, and the user has three screens, one for an overview of the whole space, one for a detailed view of some portion of the space, and one touch screen for control. Head-mounted displays, which monitor user head and body movements to give the user a complete simulated three-dimensional space view, are forms of large virtual workspaces. A problem with a single large workspace is that only a limited number of things can be adjacent to any object. The space required for the objects and their shapes constrains the manner in which the space may be arranged and how densely packed documents or data can be presented. Multiple virtual workspaces provide geometrically-oriented workspaces linked together in which a project may contain a number of views and, when active, covers the entire screen. For example, when a user maneuvers close enough to a port, the user is swept into another workspace or subworkspace.
The above techniques are examples of display systems which try to overcome the limited workspace inherent with computers that display multiple applications or documents on a two-dimensional display screen. However, these display systems do not provide a method for displaying multiple applications presented by an operating system in three dimensions. Thus, there is a need in the art for a display system which provides an enhanced system for displaying multiple applications or windows as simulated three-dimensional objects on a computer display screen.